A formed article comprising (meth)acrylic resin compositions has excellent transparency and low optical distortion, and therefore has found applications as optical lenses, substrates for discs, automobile parts, signboards, name plates, lighting covers, light guide plates and the like.
As one of methods for producing a (meth)acrylic resin composition, known is a method comprising continuously feeding a liquid starting material comprising a polymerizable monomer, a polymerization initiator and the like into a tank reactor for bulk polymerization while continuously discharging a reaction product (hereinafter, the method is sometimes called the continuous bulk polymerization mode). The continuous bulk polymerization mode is suitable for mass production of a (meth)acrylic resin composition having excellent optical properties.
In the continuous bulk polymerization mode, operation is sometimes halted for cleaning or replacing components, for example. When operation is halted, the temperature of the reaction solution within the polymerization tank is lowered for preventing oxidation and degradation of the resin and, when necessary, the entire reaction solution is discharged from the polymerization tank. These processes require additional steps and time until operation resumes, and also end up wasting raw materials and heat, contributing to an increase in production costs. As a prevention measures, Patent Document 1 discloses use of a chain transfer agent in order to enable the reaction solution within the tank reactor to maintain its amount, its temperature, and its polymerization conversion ratio constant during the halted feeding of the polymerizable monomer and the polymerization initiator.